One of the most interesting sources related to the presence of Europeans in Japan during the sixteenth and seventeenth centuries is, in my opinion, the De Missione Legatorum Iaponensium ad Romanam curiam, or the Dialogue Concerning the Mission of the Japanese Ambassadors to the Roman Curia, as it has been beautifully translated by J. F. Moran and edited by Derek Massarella in 2012.
Among the many fascinating aspects of this work, one that has been disputed by some historians in the last few decades has been of its authorship. On the Portuguese side, Américo da Costa Ramalho and others defend that the Portuguese Jesuit Duarte de Sande was responsible for penning the dialogue. Even the National Library of Portugal lists Sande as its author. Meanwhile, on the other side, J. F. Moran and others defend the old thesis that Alessandro Valignano, the Italian Jesuit Visitor to the Asian missions in the period, was the one behind its inception.
As very few contemporary sources refer to the Dialogue, and even fewer comment on its authorship — maybe none? — it is almost impossible to define this dispute without giving in to some level of patriotic pride.
Marginalia can be, though, of some help here. As we all know, it is not uncommon to find notes taken on these books, especially on their covers. Often, they refer to the library’s name where the book is kept, or their owner. For example, the copy kept now at the library of the Universidad Complutense de Madrid was clearly owned before by the Jesuit library in Alcalá, as we can see in its cover. It even has a date, 1705, probably indicating the year when it entered the Jesuit collection.
Google Books has recently digitized the copy kept at the Italian Casanatense Library, in Rome. This copy was, however, ignored by most researchers dealing with this book. For example, Aurelio Vargas Díaz-Toledo’s list omits its existence. Nevertheless, we must admit that his list of extant copies is far superior to the odd list by Iberian Books, which registers only the copy at the Universidad de Sevilla.
The Casanatense De Missione… is probably the only one that has an inscription referring to the authorship of the book. In the lower side of its cover, it has a Latin inscription that clearly states Valignano as the author of the book. Sande is listed as the one responsible for translating it into Latin.So, there you go. It seems that, at least for Italian Jesuits at the time, it was undoubtedly Valignano the one behind the De Missione… Point for J. F. Moran and his side.